High-Shear Mixing Apparatus

Abstract

A high shear mixing device includes a first screw kneader and a second screw kneader. Each screw kneader rotates in an opposite direction with the other screw kneader such that the blades overlap each other. One of the three blades in each of the screw kneaders is an open-type blade having through holes formed in a center of the respective blade except for an outer periphery of a rotation direction surface, and the other two blades are both closed-type blades having a closed rotation direction surface closed without a through hole. The open-type blade in the first screw kneader is positioned between the two closed-type blades in the second screw kneader. The open-type blade in the second screw kneader is positioned between the two closed-type blades in the first screw kneader.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a national phase entry under 35 U.S.C. 371 of International Application No. PCT / KR2024 / 010888 filed Jul. 26, 2024, which claims priority to Korean Patent Application No. 10-2023-0098953, filed on Jul. 28, 2023, the disclosures of which are incorporated herein by reference.TECHNICAL FIELD

[0002] The present disclosure relates to a high shear mixing device, particularly, a high shear mixing device used for preparing a dry electrode for a secondary battery.BACKGROUND

[0003] The stirring device is used to finely mix various paste manufacturing facilities and chemical raw materials, such as inks, pigments, paints, cosmetics, pharmaceuticals and paints, various coatings, abrasives, ceramics or metal powder or various electronic materials (PZT, dielectric, MLCC, ferrite, display materials). As the stirring device, in particular, as equipment for stirring high-viscosity substances, a planetary mixer that stirs high-viscosity substances in a container using a blade and a rotor is widely used.

[0004] The planetary mixer as described above is also used to prepare an electrode for a secondary battery. That is, along with the expansion of the use of the development of the secondary battery, improvements in low resistance, high capacity, mechanical properties and productivity of the electrode are continuously required, and thus the need for high shear mixing of the mixture to prepare the electrode is also increasing.

[0005] Specifically, recently, a technology for preparing a dry electrode film by mixing an active material, a binder, and an electrically conductive material without a liquid medium such as a solvent or dispersion medium, and then passing the powder mixture through a rolling roll, is being actively developed, and high shear mixing has been applied to this preparation of the electrode.

[0006] That is, in the above method, a binder called “fiberizable binder” or “fiber-forming binder” is used. If high shear mixing is applied to the mixture containing the binder, the binder is micro-fiberized to adhere the active material and the electrically conductive material.

[0007] However, in this high shear mixing process, the fiberizable polymer becomes chewing gum-like state, and a high load is applied to the high shear mixing device, and thus the high shear mixing device is often damaged. Meanwhile, if the shear force is lowered to prevent damage to the equipment as described above, fiberization of the fiberizable polymer is not performed well. Accordingly, due to these problems, it is very difficult to constitute the high shear mixing device as a mass-production equipment for preparing a dry electrode for a secondary battery.PRIOR ART DOCUMENTPatent Document(Patent Document 1) Korean Laid-open Patent Publication No. 10-2011-0117902Technical Problem

[0009] The present disclosure has been devised to solve the above problems in the prior art, and it is an object of the present disclosure to provide a high shear mixing device capable of efficiently mixing materials without overload when mixing materials by high shear force.

[0010] In particular, it is an object of the present disclosure to provide a high shear mixing device capable of efficiently micro-fiberizing the polymer without overload during high shear mixing of a mixture for preparing a dry electrode comprising a fiberizable polymer as a binder.Technical Solution

[0011] In order to achieve the above object, the present disclosure provides a high shear mixing device comprising,

[0012] a first screw kneader and a second screw kneader;

[0013] a first rotation driving mechanism for rotating the first screw kneader and a second rotation driving mechanism for rotating the second screw kneader;

[0014] a revolution driving mechanism in which the first rotation driving mechanism and the second rotation driving mechanism are rotatably installed;

[0015] a driving mechanism body in which the revolution driving mechanism is installed; and

[0016] a mixing tank,

[0017] wherein each of the first screw kneader and the second screw kneader comprises a shaft whose one end is connected to the rotation driving mechanism; and three blades having one end fixed to the shaft and having a body spirally curved along a longitudinal direction of the shaft, and

[0018] wherein each of screw kneaders rotates in opposite directions with the other screw kneaders and the blades overlapping each other,

[0019] wherein one of the three blades provided in each of the first screw kneader and the second screw kneader is an open-type blade having through holes formed in the center except for the outer periphery of the rotation direction surface, and the other two blades are both closed-type blades having the rotation direction surface closed without a through hole,

[0020] wherein the open-type blade provided in the first screw kneader is overlapped between the two closed-type blades provided in the second screw kneader, and wherein the open-type blade provided in the second screw kneader is overlapped between the two closed-type blades provided in the first screw kneader

[0021] In one aspect of the present disclosure, the high shear mixing device has a feature that the screw kneaders rotate by a rotation driving mechanism and revolve by the revolution driving mechanisms.

[0022] In one aspect of the present disclosure, the through hole formed in each blade may be formed to extend to the outer peripheral surface of the shaft.

[0023] In one aspect of the present disclosure, the rotation direction distal end of the blade provided in the first screw kneader and the second screw kneaders may be rotated while maintaining a separation distance of 1 mm to 10 mm from other screw kneaders.

[0024] In one aspect of the present disclosure, the high shear mixing device is used for high shear mixing of a mixture for preparing a dry electrode containing a fiberizable polymer as a binder, and thus may be used for micro-fiberizing the fiberizable polymer.Advantageous Effects

[0025] The high shear mixing device of the present disclosure provides an effect capable of efficiently mixing materials without overload when mixing materials by high shear force. In addition, since damage to the device is minimized by this effect, it has a feature that it is possible to configure the device in a large capacity.

[0026] In particular, the high shear mixing device of the present disclosure provides an effect of efficiently micro-fiberizing the polymer without overload during high shear mixing of a mixture for preparing a dry electrode containing a fiberizable polymer as a binder.BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a perspective view showing one aspect of a high shear mixing device of the present disclosure.

[0028] FIG. 2 is a perspective view showing one aspect of a screw kneader provided in the high shear mixing device of the present disclosure.

[0029] FIG. 3 is a simplified drawing illustrating the overlapped structure of the screw kneader shown in FIG. 2.

[0030] FIG. 4 is a perspective view illustrating the overlapped structure of a screw kneader of the comparative example having a different overlapped structure from the screw kneader of the present disclosure.

[0031] FIG. 5 is a simplified diagram illustrating the overlapped structure of the screw kneader shown in FIG. 4.DETAILED DESCRIPTION

[0032] Hereinafter, examples of the present disclosure will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily carry out the present disclosure. However, the present disclosure may be embodied in many different forms and is not limited to the examples described herein. Throughout the specification, like reference numerals are assigned to similar parts.

[0033] FIG. 1 is a perspective view showing one aspect of a high shear mixing device 100 of the present disclosure, and FIG. 2 is a perspective view illustrating one aspect of a screw kneader provided in the high shear mixing device of the present disclosure, and FIG. 3 is a simplified view of the overlapping structure of the screw kneader illustrated in FIG. 2.

[0034] The high shear mixing device 100 of the present disclosure, as shown in FIG. 1, comprises

[0035] the first screw kneader 10 and the second screw kneader 10′; the first rotation driving mechanism 21 for rotating the first screw kneader and the second rotation driving mechanism 21′ for rotating the second screw kneader; the revolution driving mechanism 23 in which the first rotation driving mechanism 21 and the second rotation driving mechanism 21′ are rotatably installed; the driving mechanism body 20 in which the revolution driving mechanism 23 is installed; and the mixing tank 30,

[0036] wherein each of the first screw kneader 10 and the second screw kneader 10′ comprises shafts 13 and 13′ whose one end is connected to the rotation driving mechanisms 21 and 21′; and three blades 15 and 15′ having one end fixed to the shaft and having a spirally curved body along the longitudinal direction of the shaft, and

[0037] wherein each of the screw kneaders 10 and 10′, as shown in FIG. 2, rotates in opposite directions with the other screw kneaders and blades 15 and 15′ overlapping each other.

[0038] As shown in FIGS. 2 and 3, one of the three blades provided in each of the first screw kneader 10 and the second screw kneader 10′ is an open-type blade having through holes 18, 18′ formed in the center except for the outer periphery of the rotation direction surface, and the other two blades are both closed-type blades having the rotation direction surface closed without a through hole,

[0039] wherein the open-type blade provided in the first screw kneader is overlapped between the two closed-type blades provided in the second screw kneader, and wherein the open-type blade provided in the second screw kneader is overlapped between the two closed-type blades provided in the first screw kneader, as shown in FIGS. 2 and 3.

[0040] When the screw kneaders rotate and engage with each other, they are characterized by revolving in the opposite direction to the direction in which the mixtures are discharged.

[0041] The high shear mixing of the present disclosure may be particularly preferably used for preparing a dry electrode for a secondary battery. That is, when preparing a dry electrode for a secondary battery, the high shear mixing device produces a freestanding electrode through a process of high shear mixing the mixture comprising an active material, an electrically conductive material, and a fiberizable binder such as PTFE as a binder to fiberize the binder, and rolling the prepared mixture. During this high shear mixing process, the fiberizable polymer becomes chewing gum-like state and a high load is applied to the high shear mixing device, which often damages the equipment. On the other hand, if the shear force is lowered to prevent damage to the equipment as described above, fiberization of the fiberizable polymer is not performed well. Therefore, due to these problems, it is very difficult to constitute a high shear mixing device as a large-capacity mass-production equipment for preparing a dry electrode for a secondary battery.

[0042] However, if the high shear mixing device of the present disclosure is used, while the dispersibility of the mixture is greatly improved and the micro-fiberization of the fiberizable polymer is effectively achieved, there is no heavy load on the device. Therefore, the high shear mixing device of the present disclosure can be preferably used in high shear mixing for preparing a dry electrode for a secondary battery, and makes it possible to constitute a large-capacity mass-production equipment.

[0043] If the high shear mixing device of the present disclosure is used, while continuously applying a high-shear force of 10 to 500 N·m to the mixture comprising an active material, an electrically conductive material, and a fiberizable binder such as PTFE as a binder, it is possible to prepare the mixture for a freestanding electrode having good quality without damage to the equipment. In addition, in the case of rolling such mixture, a freestanding electrode having excellent tensile strength is prepared, and when a battery is constituted by such an electrode, the lifetime of the battery is greatly improved.

[0044] In particular, the inventors of the present disclosure have discovered that, as shown in FIGS. 4 and 5, if the open-type blade provided in the first screw kneader is overlapped between the open-type and closed-type blades provided in the second screw kneader, and the open-type blade provided in the second screw kneader is overlapped between the open-type and closed-type blades provided in the first screw kneader, the open-type blades overlap each other, so that the through holes 18, 18′ overlap each other, and the material to be mixed passes through the through holes 18, 18′ without being subjected to shear force, and thus the high shear mixing effect is deteriorated; and completed the present disclosure for improving this problem.

[0045] In other words, the inventors of the present disclosure have found that, as shown in FIGS. 2 and 3, if the open-type blade provided in the first screw kneader is overlapped between two closed-type blades provided in the second screw kneader, and the open-type blade provided in the second screw kneader is overlapped between two closed-type blades provided in the first screw kneader, the high shear mixing is maximized and the load applied to the high shear mixing device is reduced, and accordingly, when the electrode is manufactured using the mixture prepared by the high shear mixing device, the lifetime characteristic of the lithium secondary battery is improved, thereby completing the present disclosure.

[0046] In one aspect of the present disclosure, one end of the body of the blades 15 and 15′ is coupled to the shaft in a spiral shape in the longitudinal direction, and accordingly, the body surface in the rotational direction may have a shape that is spirally bent along the longitudinal direction of the shaft.

[0047] In the present disclosure, the body of the blades 15 and 15′ may have a shape in which the body having a shape of a circular plate with one end cut off, an oval plate with one end cut off or a polygonal plate is spirally bent along the longitudinal direction of the shafts 13 and 13′. In the case of the circular plate and the oval plate, the cut-off portion may be coupled to the shaft in a spiral shape in the longitudinal direction, and in the case of the polygonal plate, one edge may be coupled to the shaft in a spiral shape in the longitudinal direction. In addition, the body may also have a shape in which the exemplified shape is partially modified to be advantageous for high shear mixing. If the body has the polygonal shape, it may be a polygonal shape such as a triangle, a quadrangle, a pentagon, and a hexagon, and is not particularly limited. However, a rectangular shape may be more preferably used.

[0048] In one aspect of the present disclosure, the high shear mixing device 100 has a feature that the screw kneaders 10 and 10′ rotate by the rotation driving mechanisms 21 and revolve by the revolution driving mechanism 23. In addition, when the screw kneaders rotate and engage with each other, they are characterized by revolving in the opposite direction to the direction in which the mixtures are discharged. As described above, if the screw kneaders rotate and revolve at the same time, the mixture is more uniformly mixed and high shear mixing can be performed more efficiently, which is preferable.

[0049] The through holes 18 and 18′ formed in the blades 15 and 15′ of the first screw kneader 10 and the second screw kneader 10′ shown in FIG. 2 represent shapes in which a through hole is formed in the center except for the outer periphery of the rotation direction surface of the blade, and in particular, the shape represents a shape in which the through hole extends to the outer peripheral surface of the shaft.

[0050] In one aspect of the present disclosure, the area of the through holes 18 and 18′ may be formed to be 40 to 80%, more preferably 50 to 70% relative to the total area of the rotation direction surface of the blade body. If the through hole is formed within the above range, it is preferable because the mixture is effectively mixed without applying a high load to the device. In particular, within the above range, micro-fiberization of the fiberizable polymer can also be effectively achieved.

[0051] If the high shear mixing device comprises the first screw kneader 10 and the second screw kneader 10′ shown in FIGS. 2 and 3, the dispersibility of the mixture is greatly improved, and fiberization of a fiberizable polymer such as PTFE is effectively achieved. In addition, during the fiberization process of the fiberizable polymer such as PTFE, a large load is not applied to the device. Therefore, the high shear mixing device of the present disclosure can be preferably used in high shear mixing for preparing a dry electrode for a secondary battery, and makes it possible to constitute a large-capacity mass-production equipment.

[0052] In particular, if a dry freestanding electrode is prepared by high shear mixing the mixture comprising an active material, an electrically conductive material, and a fiberizable binder such as PTFE as a binder and rolling such mixture, the tensile strength of the freestanding electrode is greatly improved, and this dry freestanding electrode provides the effect of greatly improving the lifetime of the secondary battery.

[0053] In one aspect of the present disclosure, it may be preferable that the rotation direction distal ends of the blades provided in the first screw kneader and the second screw kneader rotate while maintaining a separation distance of 1 mm to 10 mm, preferably 1 mm to 5 mm, more preferably 1 mm to 3 mm from other screw kneaders. When having the above separation distance, fiberization of a fiberizable polymer such as PTFE is effectively achieved, and the high shear mixing device is not subjected to a large load that may damage the device, and thus it is possible to efficiently prepare a freestanding electrode of good quality.

[0054] In one aspect of the present disclosure, it is more preferable that the rotational speed of the first screw kneader and the second screw kneader is 10 rpm to 500 rpm, preferably 10 rpm to 300 rpm, more preferably 10 rpm to 150 rpm. If high shear mixing is performed at the above speed, fiberization of a fiberizable polymer such as PTFE is effectively achieved, the high shear mixing device is not subjected to a large load that may damage the device, and thus it is possible to efficiently prepare a freestanding electrode of good quality. In addition, revolution speed may be 5 rpm to 100 rpm, preferably 10 rpm to 50 rpm, more preferably 10 rpm to 30 rpm.EXAMPLES

[0055] Hereinafter, the present disclosure will be described in detail by way of example in order to specifically explain the present disclosure. However, the examples according to the present disclosure may be modified in various other forms, and the scope of the present disclosure should not be construed as being limited to the examples described in detail below. The examples of the present disclosure are provided to more completely explain the present disclosure to those of ordinary skill in the art.Example 1: Preparation of Freestanding Electrodes by High Shear Mixing Device

[0056] 95.5% by weight or 97% by weight of NCM powder, which is particles of positive electrode active material with an average particle diameter of 10 μm (Product name: GL80, LG Chem company), 1.5% by weight of Li250 (Denka company) as an electrically conductive material and PTFE as binder (1.5% by weight or 3% by weight) was mixed to prepare a mixture for a freestanding electrode.

[0057] The high shear mixing device of the present disclosure was constituted as shown in Table 1 below, and high shear mixing was performed for 2 minutes by applying a shear force of 100 N·m to the mixture at 90° C. at the rotation of 30 rpm and revolution of 15 rpm.

[0058] Next, the secondary mixture in the form of dough prepared above was milled at 100° C. with a two roll mill (MR-3, Inoue company) to prepare a free-standing film having a thickness of 200 μm.

[0059] Thereafter, the free-standing film was placed on one side of a Primer Coated Aluminum Foil (Manufactured by Dongwon Systems company) current collector having a thickness of 20 μm, and bonded through a lamination roll maintained at 120° C. to prepare a positive electrode.TABLE 1Constitution of high shear mixing deviceArrangementof first andRotationBindersecondof screwMixingcontentShape of screw kneaderscrew bladekneadervolume(wt %)Examplefirstfirst blade isshapeoverlaprevolution +1.5 L1.51screwopen-type (throughofrotationkneaderhole formation)FIGS.and second and2 andthird blades are3closed-typesecondfirst blade isscrewopen-type (throughkneaderhole formation)and second andthird blades areclosed-typeExamplefirstfirst blade isshapeoverlaprevolution +1.5 L3.02screwopen-type (throughofrotationkneaderhole formation)FIGS.and second and2 andthird blades are3closed-typesecondfirst blade isscrewopen-type (throughkneaderhole formation)and second andthird blades areclosed-typeCompara-firstfirst blade isshapeoverlaprevolution +1.5 L1.5tivescrewopen-type (throughofrotationExamplekneaderhole formation)FIGS.1and second and4 andthird blades are5closed-typesecondfirst blade isscrewopen-type (throughkneaderhole formation)and second andthird blades areclosed-typeCompara-firstfirst blade isshapeoverlaprevolution +1.5 L3.0tivescrewopen-type (throughofrotationExamplekneaderhole formation)FIGS.2and second and4 andthird blades are5closed-typesecondfirst blade isscrewopen-type (throughkneaderhole formation)and second andthird blades areclosed-type(Note)Overlap: The rotation direction distal ends of the blades provided on the first screw kneader and the second screw kneader maintain a separation distance of 3 mm from the other screw kneadersExperimental Example 1: Measurement of Tensile Strength of Freestanding Electrode

[0060] The tensile strength of the freestanding electrodes prepared in Examples 1 to 2 and Comparative Examples 1 to 2 was measured at a condition of 50 mm / min by a 180 degrees peel measurement method using UTM equipment of LLOYD company. At the time of the measurement, the maximum value of the force applied up to the point in time when the film did not break was evaluated as the strength of the free-standing film, and the measurement results are shown in Table 2 below.TABLE 2ExampleExampleComparativeComparative12Example 1Example 2Tensile6.867.346.476.98Strength (MPa)Experimental Example 2: Evaluation of Lifetime Characteristic of Battery(1) Manufacture of Lithium Secondary Battery

[0061] The positive electrodes prepared in Examples 1 to 2 and Comparative Examples 1 to 2 were used, lithium metal was used as a counter electrode, and an electrolyte solution containing 1M LiPF6 in a solvent containing EC:DMC:DEC (volume ratio of 1:2:1) was used, to manufacture a coin-type half-cell.(2) Evaluation of Capacity Retention Rate of Lithium Secondary Battery

[0062] After charging and discharging the coin-type half battery prepared above 100 times at 25° C. under the voltage range of 3 to 4.3 V and the current condition of 0.33 C-rate, the retention rate of the 100th discharging capacity compared to the 1st discharging capacity was calculated, and the results are shown in Table 3 belowTABLE 3ExampleExampleComparativeComparative12Example 1Example 2Capacity retention98.597.796.896.1rate 0.33 / 0.33 C,Room temperaturelife (Capa.Efficiency,% @100th cycle)

[0063] Although the present disclosure has been described with reference to the above-mentioned preferred examples, various modifications and variations can be made without departing from the spirit and scope of the disclosure. Accordingly, the appended claims will cover such modifications and variations as long as they fall within the gist of the present disclosure.DESCRIPTION OF SYMBOLS10: First screw kneader

[0065] 10′: Second screw kneader

[0066] 13, 13′: Shaft

[0067] 15, 15′: Blade

[0068] 18,18′: Through hole

[0069] 20: Driving mechanism body

[0070] 21: First rotation driving mechanism

[0071] 21′: Second rotation driving mechanism

[0072] 23: Revolution driving mechanism

[0073] 30: Mixing tank

Claims

1. A high shear mixing device, comprising:a first screw kneader and a second screw kneader;a first rotation driving mechanism for rotating the first screw kneader and a second rotation driving mechanism for rotating the second screw kneader;a revolution driving mechanism in which the first rotation driving mechanism and the second rotation driving mechanism are rotatably installed;a driving mechanism body in which the revolution driving mechanism is installed; anda mixing tank,wherein:each of the first screw kneader and the second screw kneader comprises a shaft and three blades, the shaft including one end connected to the rotation driving mechanism and each of the three blades having one end fixed to the shaft and having a body spirally curved along a longitudinal direction of the shaft,each of the first and the second screw kneaders is configured to rotates in an opposite directions to the other screw kneader such that the three blades of each of the first and the second screw kneaders overlap each other,one blade of the three blades in each of the first screw kneader and the second screw kneader is an open-type blade having through holes formed in a center of the respective blade except for an outer periphery of a rotation direction surface of the blade, and the other two blades of the three blades are both closed-type blades having a closed rotation direction surface without a through hole,the open-type blade in the first screw kneader is positioned between the two closed-type blades in the second screw kneader, andthe open-type blade in the second screw kneader is positioned between the two closed-type blades in the first screw kneader.

2. The high shear mixing device according to claim 1, wherein the first and the second screw kneaders rotate by the first and the second rotation driving mechanisms and revolve by the revolution driving mechanism.

3. The high shear mixing device according to claim 1, wherein a shape of each of the through holes formed in the blades extends to an outer peripheral surface of the shaft.

4. The high shear mixing device according to claim 1, wherein rotation direction distal ends of each of the blades in the first screw kneader and the second screw kneader rotate while maintaining a separation distance ranging from 1 mm to 10 mm from other screw kneaders.

5. The high shear mixing device according to claim 1, wherein the high shear mixing device is configured to micro-fiberize a fiberizable polymer by high shear mixing a mixture for preparing a dry electrode containing the fiberizable polymer as a binder.

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